An investigation was made of samples having a chemical formula of Ni1-x Zn (x) Fe2O4, where x = 0.3, 0.5 and 0.7. The samples were prepared by the reaction combustion synthesis method and sintered at 1,200 degrees C/2 h in a static air atmosphere. The influence of the Zn concentration on the relative density, microstructure and magnetic properties of the samples was studied. X-ray diffraction, scanning electron microscopy and magnetic hysteresis loop tracer were used to analyze the compositions. The samples were found to have a spinel cubic structure, sintered density of 92.9%-98.8% of the corresponding X-ray density, homogeneous microstructure with grain size ranging from 1.37 to 3.36 mu m, maximum flux density of 0.16-0.35 T, field coercivity ranging from 17 to 168 A/m, and loss hysteresis of 1.5-105 W/kg. Increased grain growth, with fine pores inside the grains, was found to occur as the Zn concentration increased. The overall findings are discussed here in light of the existing understanding of these systems.